FEI Quanta FEG 250, User'S Operation Manual

Page: 137 / 228

Maintenance and Troubleshooting: The Standard Insert
8-5
FIGURE 8-3 REMOVING AND DISASSEMBLING THE INSERT
3. Inspect the o-ring at the bottom of the insert. If the o-ring looks
deformed or damaged, replace it. This is a critical seal between
EC1 and EC2 (which is under very low pressure). The surface of
the o-ring must be flush against the insert.
4. Inspect the threads on the insert for dirt, scratches on the threads,
etc. Clean the insert threads and if damaged, replace the insert.
HOUSING CLEANING
Once the entire assembly has been removed and taken apart:
1. Clean the standard insert housing with a toothbrush and Soft
Scrub/CIF or aluminous powder.
2. Rinse with de-ionized or distilled water.
3. Rinse in alcohol or isopropanol and dry with clean compressed air.
Under normal use, the insert should be inspected only when being
inserted. It should only be removed for cleaning when indicated by
poor astigmatism.
PLATINUM APERTURES CLEANING
• Method 1:
Heat the aperture (held in special tweezers with platinum points) in
a clean gas flame until red-hot (for 4–20 seconds). Take care that
the aperture does not melt or become stuck to the tweezers.
• Method 2:
Connect a V-shaped molybdenum foil boat (about 2 cm long)
across the low voltage / high current contacts of a Vacuum
Evaporator unit. Use a pressure of 1.3x10
-3
Pa (1x10
-5
Torr) and
heat until white hot to flash decontaminate. Do not allow the
Vacuum Evaporator to contact the atmosphere until the foil boat is
cool. When the aperture has cooled down, place it on the foil,
vacate, and reheat the foil to red heat on the aperture (for 4–20
seconds). Take care that the aperture does not melt or become
stuck to the foil. Again, do not allow the Vacuum Evaporator to
contact the atmosphere until the foil boat and aperture is cool.
C a u t i o n !
Do not attempt to clean apertures just by washing in solvent, as this can
have an adverse affect just by shifting contamination back onto the aperture.
Aperture
Positioning
Tool
Housing
Final Aperture
+ c-clip